One electrophotographic color printer well known in the art is a tandem type color laser printer equipped with four photosensitive drums and four developing cartridges. The photosensitive drums are juxtaposed corresponding to each color of yellow, magenta, cyan, and black. Each of the developing cartridges supplies toner to the corresponding photosensitive drum.
As a developing cartridge provided in such a tandem type color laser printer, there has been proposed a developing cartridge including a developing roller and a supply roller that is in contact with the developing roller. When the developing cartridge is mounted in a drum cartridge in which the photosensitive drum is rotatably supported, the developing cartridge is pressed against a photosensitive drum so that the developing roller is in pressure contact with the photosensitive drum.
Such a conventional developing cartridge includes a bias electrode that is brought into contact with a relay electrode provided at the drum cartridge when the developing cartridge is mounted in the drum cartridge. Bias voltage applied by a high-voltage power supply provided at a main casing of the printer is applied to the bias electrode of the developing cartridge via the relay electrode of the drum cartridge.